The present invention relates to paper handling. More specifically, the invention relates to folding and manipulation of stapled documents.
One commonly used method of permanently fixing multiple pages is stapling of the pages. When print jobs are produced by laser printing, photocopying and other short-run processes, it may be desired to fold or otherwise manipulate assembled documents. In the prior art, this was either done by hand, or by the use of paper handling equipment, such as sheet folders.
One of the aspects of sheet folders is that it was necessary to separately align individual documents. This increased the expense of paper folding equipment. In addition, the staples present alignment problems, particularly if staples are to be in alignment with the fold. Generally, the fold should occur along a staple line.
In the case of documents which are produced by the use of laser printers or photocopiers, any additional procedures involved in producing a final product, such as folding equipment, require the use of additional equipment. This additional equipment would be either within the printer or external to the printer, but in either case requiring additional expense and bulk. That means that the ability of providing office printers which are capable of providing assembled booklets or other multi-page brochures is limited. It would be desired to provide a printer arrangement which allows assembly of multiple sheets of paper or other sheet media, but does not require a substantial investment in additional equipment for folding and other paper handling purposes. It is desired that the additional features be provided without making the printer or copier substantially more complicated or less economical to operate. It is therefore desired to provide a simplified automatic paper folder for such equipment.
In providing such a paper folder, it is important that the staples be aligned when using a folding blade or other creasing device. If the staples are not aligned, the folding line will occur at the wrong position on the document. While having the staples in a staple line collinear to a fold is a minor inconvenience; an angular misalignment creates an unsightly appearance and is also objectionable to readers of the document. Angular misalignment is more critical and can result in the staples being skewed, as well as the folded document itself being skewed with respect to itself. Thus, if an 11xe2x80x3xc3x9717xe2x80x3 ledger or (double letter size, 27.94xc3x9743.18 cm) document is folded to form two letter size halves per sheet, a 1xc2x0 misalignment will result in an offset in the x and y directions of 4.8 mm and 3.8 mm, respectively. FIG. 1 shows the results of misalignment of such a job in millimeters of offset versus angular alignment when using ledger size sheets.
In the prior art, mechanical force is used to transmit motion to a xe2x80x9cfeeding bladexe2x80x9d or to create a xe2x80x9cbucklexe2x80x9d in the sheets. This requires either a motor or additional mechanism to cause this mechanical force. The feeding blade can get stuck between folding rollers, especially when folding documents having large numbers of sheets. At that point, a high force is needed to release the feeding blade and causes the document to be marked by the exertion of the release force. It is also necessary to position the job extremely accurately; otherwise, the folding line will not be centered or will not be perpendicular, causing an unacceptable booklet quality.
In addition, the paper folding mechanism must, prior to folding the documents, transport the documents to an appropriate location for folding. This means that, often after the documents are assembled or otherwise sorted at a discharge end of a printer, these documents must again be handled. This can result in mishandling of the documents and of course results in increased complexity of the equipment.
In describing the invention, the term xe2x80x9cpaperxe2x80x9d is used to describe paper, as well as other forms of sheet media. xe2x80x9cDocumentxe2x80x9d is intended to describe one or more sheets which may be in the form of a booklet. A xe2x80x9cprint jobxe2x80x9d may include multiple copies of a document. A document can take a number of forms, but is often an assembly of sheets of paper or other sheet media. In this invention, the documents are generally bound by a row of staples. Typically, this is a xe2x80x9cbooklet,xe2x80x9d sometimes called xe2x80x9csaddle stitch and fold.xe2x80x9d A booklet has more than one page, usually two to five or more pages. It has one or more staples that hold the pages together. The staples are located along a line, approximately at the middle of the page. Unless portions of the booklet are intentionally offset, and after the pages are stapled, the pages are folded along a staple line, meaning a line defined by the staples.
Typically, the process to make a booklet is to add a set of staples, usually in the middle of the sheet, as shown in FIG. 2. Once the document is stapled, it is folded at the center line so that it has a book appearance, as shown in FIG. 3. In a xe2x80x9cfeeding bladexe2x80x9d approach, a document is positioned extremely accurately, so that the staples are nearly exactly above a feeding blade and below a nip defined by a pair of folding rollers. The feeding blade is then shifted toward the nip in order to feed the stack of papers toward the nip of the folding rollers. By friction, the folding rollers grab the stack. At this time, the blade retracts back to its original position away from the nip, thereby avoiding the feeding blade being trapped by the feeding rollers. This procedure is shown in FIGS. 4 and 5.
There are two key points in the process in which accuracy is essential. The first is when the blade initiates the feeding movement. At that time, the staples must be precisely aligned with the blade. If this does not occur, the folding line will be at the wrong position, or diagonal to the edge of the stack. This would make the booklet unacceptable. This misalignment is shown in FIG. 6, and is important in order to achieve a proper print job. The misalignment can be characterized, referring to FIG. 6, by the following equations:
FIG. 6. Impact of the Alignment of the Job                               a          +          b                =        l                            xe2x80x83                                      sin          ⁢                      xe2x80x83                    ⁢          θ                =                  y          b                                                  tan          ⁢                      xe2x80x83                    ⁢          θ                =                                                            (                                  b                  -                  a                                )                            2                                      h              2                                =                                    b              -              a                        h                                              xe2x80x83                                      sin          ⁢                      xe2x80x83                    ⁢          θ                =                              2            ⁢            y                                              h              ⁢                              xe2x80x83                            ⁢              tan              ⁢                              xe2x80x83                            ⁢              θ                        +            1                                                            tan          ⁢                      xe2x80x83                    ⁢          θ                =                                            2              ⁢              b                        -            1                    h                                    xe2x80x83                            y        =                                            h              ⁢                              xe2x80x83                            ⁢              sin              ⁢                              xe2x80x83                            ⁢              θ              ⁢                              xe2x80x83                            ⁢              tan              ⁢                              xe2x80x83                            ⁢              θ                        +                          1              ⁢                              xe2x80x83                            ⁢              sin              ⁢                              xe2x80x83                            ⁢              θ                                2                                        b        =                                                            h                ⁢                                  xe2x80x83                                ⁢                tan                ⁢                                  xe2x80x83                                ⁢                θ                            +              1                                      xe2x80x83                                ⁢          2                                    xe2x80x83                            xe2x80x83                                          cos          ⁢                      xe2x80x83                    ⁢          θ                =                                            x              +              a                        b                    =                                    x              +              1              -              b                        b                                              xe2x80x83                            xe2x80x83                                          1          +                      cos            ⁢                          xe2x80x83                        ⁢            θ                          =                              2            ⁢                          (                              x                +                1                            )                                                          h              ⁢                              xe2x80x83                            ⁢              tan              ⁢                              xe2x80x83                            ⁢              θ                        +            1                                              xe2x80x83                            xe2x80x83                                                                                    (                                  1                  +                                      cos                    ⁢                                          xe2x80x83                                        ⁢                    θ                                                  )                            ⁢                              (                                                      h                    ⁢                                          xe2x80x83                                        ⁢                    tan                    ⁢                                          xe2x80x83                                        ⁢                    θ                                    +                  1                                )                                      2                    -          1                =        x                            xe2x80x83                            xe2x80x83                                x        =                                                            h                ⁡                                  (                                                            sin                      ⁢                                              xe2x80x83                                            ⁢                      θ                                        +                                          tan                      ⁢                                              xe2x80x83                                            ⁢                      θ                                                        )                                            +                              (                                  1                  +                                      cos                    ⁢                                          xe2x80x83                                        ⁢                    θ                                                  )                                      2                    ⁢          1                                    xe2x80x83                            xe2x80x83            
According to these equations, a 1xc2x0 misalignment when folding an 11xe2x80x3xc3x9717xe2x80x3 (ledger size or double letter size sheet) would represent an offset of
x=4.8 mm
y=3.8 mm
FIG. 1 shows the behavior of the variables x and y, when the angle varies from 0xc2x0 to 20xc2x0 in a ledger size booklet. The steep slope of these lines is notable.
In another prior art technique, a xe2x80x9cbuckle approachxe2x80x9d is used. This is schematically shown in FIGS. 7. In FIGS. 7A and B, a stack of sheets is fed until the leading edges of the sheet find a stop. As the feeding process continues, the stack is forced to deform upwards, as shown in FIGS. 7C and D, creating a buckle. When the buckle is high enough, it contacts a pair of folding rollers, which by friction grabs the stack and creates the folding line, as shown in FIGS. 7D-F. This method has the disadvantage of being hard to control with respect to accuracy of the alignment of the folding line. This is particularly problematic with respect to linear alignment, although angular alignment also creates problems.
In accordance with the present invention, magnetic forces are used in order to manipulate assembled documents for further processing. This is accomplished by using the ferromagnetic characteristics of binding elements of the document, typically staples, in order to accomplish such manipulation. The magnets, because they are able to align with the staples, use the previously established registration of stapled jobs in order to provide a controlled and neat stack of multiple paper documents. The magnets permit transportation of stapled documents in order to sort the documents or for sending the documents to a different location. It is also possible to use the magnets to rotate documents, flip (invert) the documents, and feed the documents in order to perform additional finishing operations. In general, the invention provides a convenient way to handle and control a stapled document as needed.
In a further aspect of the invention, the magnetic force is used to establish a registration of a fold line, by lifting a document along a staple line, thereby establishing the fold line at the staple line and in alignment with the staple line.
Magnetic force is substituted for mechanical force in feeding a print job into the nip of rollers. Such magnetic force may be either a permanent magnet or an electromagnet, depending upon the specific configuration of the folding mechanism. By precisely locating and distributing the magnets, it is possible to have magnets automatically align the job by actuating on the staples. This allows the folding equipment to generate a folding line precisely where required without having to position the job with the precision that current methods require. In the preferred embodiment, electromagnets are used because:
1. It is possible to control the magnetic force according to the size of the job. Since more pages imply more weight to be transported, higher magnetic force may be required.
2. There will always be a time when it is necessary to release a stack. When using an electromagnet, this operation can be as simple as deactivating it and the magnetic force will be zero, releasing the staples and the job on a predefined position or location. Additionally, electromagnets offer the possibility of degaussing the staples after the magnetic force is applied to them.
By the use of magnetic force, it is possible to move or transport stacks in any of the large number of directions, including vertical, horizontal, horizontal sideways, flip, rotate, etc.
The arrangement of a particular array of magnets would of course be dependent upon the application. For example, in the folding process to create a booklet, it is possible to provide a pair of magnets to align with pairs of staples along a staple line. This assumes that the booklet is rendered with at least two staples.
Advantages of the invention include the fact that it is possible to implement the invention without adding an additional motor or mechanical device. It is possible to avoid the use of a mechanical part which could be caught between the rollers during operation in a manner of a blade and nip arrangement. In addition, by using the magnets, it is not necessary to accurately pre-position a stack. This is because the stack will be aligned automatically by the magnetic field operating on the staples.
In addition, it is possible to have more control of the job and of the positioning of the stack. The magnetic force can be varied in order to account for the weight and friction of the stack, as well as variations in the frictional forces acting upon the stack. The magnetic force can also be used to help control the movement of the stapled document. This magnetic force can be regulated easily and can even be turned off.
In accordance with a further aspect of the invention, a nip roller arrangement is provided that in which at least one magnet is located in a position along one of the nip rollers. As the stack is moved past the nip rollers, the magnet attracts the staple and pulls the stack up between the nip rollers. This causes the stack to be folded by the nip rollers along the staple line. The job can be released either by deactivating the magnetic force or by mechanically blocking the paper path.
In a further aspect of the invention, non-stapled jobs are provided with a temporary ferromagnetic device, such as a clip. The positioning of the clip is accomplished first and is removed subsequent to the paper handling, or removed by the end-user manually.
In accordance with a further aspect of the invention, the use of magnetic force to manipulate paper documents is combined with buckling or with blade and nip roller techniques. This permits the use of such techniques while providing the advantages of alignment and ease of manipulation afforded by the use of the magnets.
In accordance with a further aspect of the invention, an array of magnets is used to lift and transport stapled documents by the staples. Further mechanisms such as folding mechanisms and sorting trays may then be used to accomplish further paper handling functions, including folding and sorting. In accordance with a further aspect of the invention, a magnetic device is used to handle a stack of documents by means of attraction of a piece of ferromagnetic material. This permits the performance of one or more complex paper handling operations.
The use of staples is normally associated with multiple sheets in a stack. It is, however, entirely possible to accomplish paper folding and other paper handling tasks when using a single sheet. Therefore, within the concept of this invention, a stack may include one or more sheets of paper. In particular, when a removable or temporary ferromagnetic clip is used, the invention can very easily function with single sheet stacks.